The present invention relates to the manufacture of cathode ray tubes and in particular to an apparatus adapted to mount color television shadow mask support pins at corner locations therein.
It has long been believed that a corner mounted rectangular shadow mask exhibits optimum performance. This belief stems from the fact that a shadow mask, when supported at its corners, will flex to follow changes in panel contour shape while providing a more stable spacing relationship to the glass. This will result in improved picture quality compared to the standard mask mounting system.
In the manufacture of conventional television bulbs, support pins are fused into the skirt portion of the panel along major and minor axes. Typically, a conventional induction heating coil is mounted in a traversing frame. A nonferrous vacuum chuck, mounted concentrically with said coil, supports the pin. Each pin is automatically loaded into the vacuum chuck. The induction coil is energized to heat the pin to an operating temperature while the traversing frame lowers itself into the panel and moves axially of the pin in the direction of the panel skirt to fuse the pin into the glass.
The conventional induction coil is water cooled and mounted on a nonferrous ceramic support. In order to deliver sufficient power to the pin for heating during the fusing operation, the coil contains a number of turns, perhaps 8 or 10, and is considerable in size.
In the past, the size of the coil has not been of particular concern since the pins were mounted in a skirt location having sufficient clearance for the coil. Now that corner mounting of support pins has become a preferred arrangement, the size of the coil is important. While details of the present invention will be outlined further in the specification, it will be mentioned here that the conventional coils are too large to properly function in the confined space of the corner areas of the television panel skirt.
Thus, the present invention provides a coil which is particularly adapted for delivering sufficient energy for heating the support pin in the corner portion of a television panel skirt.